Siemens Servo Motor Repair vs. Replace: A Comparison I Learned the Hard Way

I've been handling Siemens servo motor repair service orders for eight years. I've personally made—and documented—seven significant mistakes that totaled roughly $18,000 in wasted budget. Now I maintain the checklist our team uses before recommending a repair or a replacement. This article is the comparison I wish someone had shown me before that first mistake.

What's a Servo Motor? (And Why It's Not an Induction Motor)

What's a servo motor? In simple terms, it's a closed-loop actuator: motor, feedback device, and drive. The drive tells the motor where it should be; the encoder or resolver reports where it actually is; the drive corrects the difference. That closed loop is what makes a servo motor a servo motor.

Most Siemens servo motors are brushless servo motors. In fact, when I say servo motor to our Siemens customers, I'm talking about a Siemens synchronous motor with permanent magnets on the rotor. The rotor locks to the stator field frequency, so there's no slip. No brushes means less maintenance, but it also means the feedback device has to be aligned correctly. If a repair shop breaks that alignment, the motor will run, but not like a Siemens motor should.

According to Siemens Industry Online Support (support.industry.siemens.com, accessed 2025), a servo motor is part of a control loop: motor plus feedback plus drive. That is the definition I use every day.

The Comparison Framework: Five Ways to Compare Repair vs. Replace

Here is the framework I now use before spending a customer's money. It's not just initial price. The first two dimensions decide the purchase. The last three decide whether the purchase was smart.

Repair usually wins on initial price. New usually wins on the other four, with one big exception: lead time can go either way. Let me show you how that actually plays out.

• Initial cost
• Lead time
• Reliability and performance
• Warranty and responsibility
• Application fit

Dimension 1: Initial Cost

Repair wins here. In my experience, a legitimate Siemens servo motor repair service quote lands between 40 and 60 percent of a new motor. The problem is that the quote is only as good as the diagnosis behind it. It's tempting to think repair is always cheaper, but that's only true if the repair is the right one. I want to say we had a repair quote around $1,100 for a medium-frame Siemens motor a couple years ago, but don't quote me on the exact model or figure. New was about $1,900. We approved the repair. Six weeks later, we had paid $1,100 for the first repair, $950 for a second repair, and a full day of labor to swap the motor twice. Net loss versus buying new was around $1,450.

Why did it fail? The shop assumed the encoder was fine and quoted only a bearing replacement. The encoder had been exposed to coolant. That is the mistake I was to blame for, because I did not ask for a complete diagnostic. Saving $800 on paper cost us real money in the end.

Dimension 2: Lead Time

New can be faster than repair. That sounds backwards, but it's not. A repair shop has to clean the motor, inspect the winding, order bearings or a cable, maybe rewind it, then align the resolver and run a load test. If they have to order a part from Siemens, that adds days. Meanwhile a standard Siemens servo motor held in stock can ship the same day.

I remember a May 2023 situation where a repair shop quoted two weeks and took four weeks, or rather, closer to five with the retest after a wrong cable. A new replacement would have arrived in two days. The line was down for ten days total. Ten days of downtime made the repair route far more expensive than the new motor price. That incident changed how I think about lead time quotes.

Dimension 3: Reliability and Performance

New wins here, but not because repair shops are bad. The issue is alignment. A Siemens synchronous motor depends on the feedback device being positioned correctly relative to the rotor poles. If a repair shop replaces a resolver without the Siemens alignment procedure, the motor will run, but it will draw more current or produce less torque. On a bench, with no load, it may look perfect. In your machine, under load, it won't.

According to IEC 60034-1, a motor's rated output is tied to duty type, cooling method, and temperature class. That is why a bench test can be misleading.

I once assumed the term reconditioned meant same as original. Didn't verify. Turned out the shop installed a compatible encoder with a different resolution. The motor ran at 500 rpm nicely. The customer's indexing axis was nowhere near repeatable. We replaced the motor after a 3-day production delay. That check now sits first on the list.

Dimension 4: Warranty and Responsibility

New wins for warranty and responsibility. A new Siemens motor carries a Siemens warranty. A repair shop's warranty only covers what that shop is willing to stand behind. In both cases, the motor might be covered. What is usually not covered is the labor to remove and reinstall it, or the cost of downtime. For a critical axis, that difference matters.

If you use a Siemens authorized repair center, the warranty story shifts. That is a legitimate route, especially for obsolete motors. But for a standard Siemens synchronous motor, I still tend to favor new because the responsibility chain is simpler. One supplier, one specification, one test standard.

Dimension 5: Application Fit

Here is where the answer isn't automatic. The same repaired motor that is a risk in a servo press can be perfectly acceptable on a single roller chain conveyor.

Repair makes sense when:

• The application is low-dynamic, such as a single roller chain conveyor, a fan, or a pump.
• The failure is mechanical: bearing, shaft seal, or shaft damage.
• The feedback device is healthy, or you are prepared to add it to the repair scope.

Replacement makes more sense when:

• The application is a high-dynamic axis with tight settling times or interpolated motion.
• The failure includes the encoder, resolver, cable, or drive mismatch.
• The motor is out of support and the repair would require obsolete electrical parts.

The frustrating part is that these conditions are discoverable before you order. That is why I preach prevention over cure. A 30-minute diagnostic conversation has saved us from every costly failure I describe here.

My Actual Advice: Diagnose First, Then Choose

If I could go back and tell my younger self one thing, it would be this: do not choose between repair and replacement until you know what failed. The cheapest repair in the world is expensive if it's the wrong repair.

5 minutes of verification beats 5 days of correction.

That quote isn't just a slogan. The 12-point checklist I created after my third mistake has caught 47 potential errors in the past 18 months. The most expensive one was a repaired motor with the wrong encoder resolution, already boxed and addressed to a customer. That would have turned into a $2,300 field service trip and a second motor purchase.

What's a servo motor worth when it's repaired badly? Nothing. When it's repaired correctly, it can be a sensible alternative to buying new. The same is true for replacement. The deciding factor is not which route sounds cheaper. It's which route you can verify.

At least, that's been my experience with Siemens motors in packaging lines, material handling, and machine tools. Your application might be different. But the sequence is the same: verify, then commit.